Halcyon Years, Alastair Reynolds

Yuri Gagarin is a private investigator, who picks up small cases from his local community, runs into trouble with the local police, and generally ekes out a living as best he can. He's aboard the Halcyon - a starship, hurtling through space, carrying thousands of passengers with thousands more sleeping the journey away.

Only his usual investigative work - catching cheating spouses, and small time con artists - is about to take a turn. He's hired by a mysterious woman called Ruby Red to look into a death in one of Halcyon's most elite families . .

. and then warned off the case again by a second mysterious woman called Ruby Blue. Caught between the two, he's about to be embroiled in a murder mystery in which - at any moment - he could be the latest victim.